linux-kernel - [patch 4/5] x86/idt: Cleanup trap

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Date:   Thu, 28 May 2020 16:53:19 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org
Subject: [patch 4/5] x86/idt: Cleanup trap_init()

No point in having all the IDT cruft in trap_init(). Move it into the IDT
code, get rid of the extra global function and fixup the comments.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/include/asm/desc.h |    2 --
 arch/x86/kernel/idt.c       |   26 +++++++++++++++++++-------
 arch/x86/kernel/traps.c     |   11 -----------
 3 files changed, 19 insertions(+), 20 deletions(-)

--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -438,11 +438,9 @@ extern void idt_setup_apic_and_irq_gates
 #ifdef CONFIG_X86_64
 extern void idt_setup_early_pf(void);
 extern void idt_setup_ist_traps(void);
-extern void idt_setup_debugidt_traps(void);
 #else
 static inline void idt_setup_early_pf(void) { }
 static inline void idt_setup_ist_traps(void) { }
-static inline void idt_setup_debugidt_traps(void) { }
 #endif
 
 extern void idt_invalidate(void *addr);
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -4,6 +4,7 @@
  */
 #include <linux/interrupt.h>
 
+#include <asm/cpu_entry_area.h>
 #include <asm/traps.h>
 #include <asm/proto.h>
 #include <asm/desc.h>
@@ -299,20 +300,27 @@ void __init idt_setup_early_pf(void)
 void __init idt_setup_ist_traps(void)
 {
 	idt_setup_from_table(idt_table, ist_idts, ARRAY_SIZE(ist_idts), true);
-}
 
-/**
- * idt_setup_debugidt_traps - Initialize the debug idt table with debug traps
- */
-void __init idt_setup_debugidt_traps(void)
-{
+	/* All traps set up: Initialize the debug IDT table. */
 	memcpy(&debug_idt_table, &idt_table, IDT_DEBUG_TABLE_SIZE);
-
 	idt_setup_from_table(debug_idt_table, dbg_idts, ARRAY_SIZE(dbg_idts),
 			     false);
 }
 #endif
 
+static void idt_map_in_cea(void)
+{
+	/*
+	 * Set the IDT descriptor to a fixed read-only location in the cpu
+	 * entry area, so that the "sidt" instruction will not leak the
+	 * location of the kernel, and to defend the IDT against arbitrary
+	 * memory write vulnerabilities.
+	 */
+	cea_set_pte(CPU_ENTRY_AREA_RO_IDT_VADDR, __pa_symbol(idt_table),
+		    PAGE_KERNEL_RO);
+	idt_descr.address = CPU_ENTRY_AREA_RO_IDT;
+}
+
 /**
  * idt_setup_apic_and_irq_gates - Setup APIC/SMP and normal interrupt gates
  */
@@ -339,6 +347,10 @@ void __init idt_setup_apic_and_irq_gates
 		set_intr_gate(i, entry);
 	}
 #endif
+	/* Map IDT into CPU entry area and reload it. */
+	idt_map_in_cea();
+	load_current_idt();
+
 	idt_setup_done = true;
 }
 
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1077,20 +1077,9 @@ void __init trap_init(void)
 	idt_setup_traps();
 
 	/*
-	 * Set the IDT descriptor to a fixed read-only location, so that the
-	 * "sidt" instruction will not leak the location of the kernel, and
-	 * to defend the IDT against arbitrary memory write vulnerabilities.
-	 * It will be reloaded in cpu_init() */
-	cea_set_pte(CPU_ENTRY_AREA_RO_IDT_VADDR, __pa_symbol(idt_table),
-		    PAGE_KERNEL_RO);
-	idt_descr.address = CPU_ENTRY_AREA_RO_IDT;
-
-	/*
 	 * Should be a barrier for any external CPU state:
 	 */
 	cpu_init();
 
 	idt_setup_ist_traps();
-
-	idt_setup_debugidt_traps();
 }